I'm the Bloomberg Distinguished Professor of Biomedical Engineering, Computer Science, and Biostatistics at Johns Hopkins University. From 2005-2011 I was the Horvitz Professor of Computer Science and Director of the Center for Bioinformatics and Computational Biology at the University of Maryland, College Park. Before joining UMD, I was at The Institute for Genomic Research, where I sequenced the genomes of many bacteria, including those used in the 2001 anthrax attacks. At TIGR I was part of the Human Genome Project and the co-founder of the influenza virus sequencing project (which is when I first learned of the anti-vaccine movement). My research group develops software for DNA sequence analysis, and our (free) software is used by scientific laboratories around the globe. I did my B.A. and M.S. at Yale University, and my Ph.D. at Harvard University, and I have published over 200 scientific papers. Follow me on Facebook or Twitter (@stevensalzberg1), or just subscribe to my alternate blog, http://genome.fieldofscience.com.

Last week a scientific paper appeared that reported that eating genetically modified (GM) corn causes cancer in rats. Specifically, the scientists fed Roundup Ready® corn, or maize, to rats for two years, and reported that both females and males developed cancer and died at higher rates than controls. [Update: this study was retracted, see this link]

This is very surprising. If GM corn causes cancer, why aren’t Americans “dropping like flies,“ as one scientist asked? We’ve been eating MonsantoMonsanto‘s Roundup Ready® corn for over a decade, even if most of us aren’t aware of it. But our rates of cancer haven’t increased more than Europeans, who eat far less GM corn. Maybe the effect is limited to rats – in which case we should also have seen dramatic increases in cancer in lab rats. But we haven’t seen that either. So what’s wrong? The best way to find out is to read the paper, which I did. It turns out to be a very badly designed study, and the report itself omits many crucial details that may (and probably do) completely invalidate the findings. The scientists leading the study have a strongly biased agenda and a conflict of interest, which they failed to reveal. I’ll explain below, but meanwhile this study has already been taken up by politicians as proof (proof!) that GMO crops are harmful. As Forbes blogger Tim Worstall explained, this paper is more politics than science.

Let’s look at the study itself, which was led by Gilles-Eric Seralini (more on him below) and published last week in Food and Chemical Toxicology. (A copy of the full paper is here.) The authors studied 200 rats for 2 years, dividing them into 10 group of 20 rats each. The test rats were fed a variety of diets:

Non-GM corn comprising 33% of the diet (this was the control group).

Roundup Ready corn comprising 11%, 22%, or 33% of the food.

Roundup Ready corn that had been treated with Roundup during cultivation.

Non-GM corn but with Roundup itself added to the rats’ water.

So what happened? Well, in some groups, the rats got more cancer than controls. But not always. In fact, the authors had to cherry-pick their own data to support their conclusions. One major problem is that only 10% of the rats were controls – 10 male, 10 female. The study’s main claim is that rates of cancer were significantly higher in the rats fed GM corn. Martina Newell-McGloughlin from UC Davis, in an interview with Discovery News, said

“The type of statistical analysis they used is really a type of fishing expedition. One individual referred to it as ‘fantasy statistics.’ “

Another major problem is that there’s no dosage effect. In other words, if Seralini is right and GM food is bad for you, then more of it should be worse. But the study’s results actually contradict this hypothesis: rats fed the highest levels of GM corn lived longer than rats fed the lowest level. A third problem, as Discovery News and other sources reported, is that the rats used in this study are a special laboratory strain that is highly prone to cancer. Perhaps most damning, though, is the fact that rats fed Roundup directly had the longest survival times. As Seralini’s own Figure 1 shows, the longest-living rats in the entire study, out of all the conditions, where those that drank Roundup in their water. These rats outlived the control rats. Yum! Maybe Perrier should start selling Roundup-enhanced spring water? Seralini and colleagues struggle to explain the internal contradictions in their study. They write,

“Interestingly, in the groups of animals fed with the NK603 [Roundup Ready corn] without R[oundup] application, similar effects with respect to enhanced tumor incidence and mortality rates were observed.”

This tortured English is their way of admitting that rats did worse (“similar effects”) when fed GM corn that was grown without Roundup. They don’t want to admit that this result contradicts their central hypothesis. The study was designed to fail: the sample sizes (10 rats in each group) are so small that all the results are likely just due to chance, and none of the differences are meaningful. It’s exceedingly unlikely that the Roundup in the rats’ water made them live longer, just as it’s unlikely that Roundup Ready corn had any effect on the incidence of cancer.

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I don’t know that the study is worthless or not. If it is worthless, so are the paltry safety studies, because the number of animals used is based on OECD regulatory guidelines.

I do have a question for you Steven. If one were to hypothesize that the EPSPS transgene lead to genesis of novel microRNAs which were suited to a down-regulation of tumor suppressor genes or up-regulation of oncogenes (breast)–can you venture a guess, or perhaps point me to research to help me understand– if such novel microRNA would act based on kinetics of a drug (where there would be a dose response to initiation of neoplasia; or would the process be more analogous to a light switch, where once a certain number of the hypothetical microRNA up/downregulated the rat DNA, leading to breast cancer and any amounts in excess of this threshold would not matter…. meaning you would not see a dose response.

This article misunderstands the science: 1. A special tumor prone type of rat was used because they more easily reveal problems with feed or other substances they are exposed to. When tumors generate more in the experimental vs control group, that validates a difference between the groups. That does not mean all humans will develop cancer from GM foods.

2. You miss the point that there is something different about the GM corn vs pure roundup. Our body may be able to tolerate the roundup much better than the GM corn. One of the weaknesses of GM research has been their overlook of the difference between feeding animals a gene, a chemical, or the food with the active chemical-resistant gene. Researchers have wrongly assumed they would have the same effect.

3. While it would be nice to see larger study groups, this study appears to be of better quality than most feeding studies performed to date. Most pro-GM studies are surprisingly short in duration, while this one studied the rats over their lifetime.

4. When GM foods are unlabeled in the US, and therefor cannot be tracked, how can anyone determine if they are increasing cancer risk or causing any health problems? It can’t be done reliably until they are labeled. A good reason for labeling these foods.

All a sensiblel person need do is look through the links that the anti-GM crowd posts to realize the hilarious absence of any real data to support any of their claims.

I find it sad how easily people can be misled by the idiotweb.org section of the internet. Rely on facts and science, learn to discern credible information from bogus, and stop allowing your emotions to trump rational thought.

Can I see a 2yr safety study? Oh, I forgot– Monsanto doesn’t do those It only does studies for 90 days on 400 rats, of which the findings are published for 10. Ooops! The biotech cabal has NO DATA, NO EVIDENCE and NO SCIENCE…. the only thing they have are assumptions and PR…… Gary take your “science” to a church or a field full of dumb sheep.

As for the comment pertaining to the “conflict of interest” with regard to the researchers, need I remind you that Monsanto has performed it’s own research (for a mere 90 days, I might add, funny how it magically falls just under the time when the alarming results begin to happen), also has a “conflict of interest” by testing their own products (“fox guarding the henhouse”, come to mind?) Furthermore, this is not the only test to show that there is a link between health risks and GE plants. As for the ridiculous comment about “why aren’t we dropping like flies”… in case you were sleeping, cancer is beginning to surpass heart disease as the number one killer in this country and in 18 states, cancer is the number one killer. And from January 2012 until now, over 400,000 people have died from cancer in this country just this year. Is that enough “dying like flies” for you? OOOOPS!

Forbes ! I’m appalled & must object that you support such deceptive journalism to sway American to keep eating GMOs, when many studies finding harm worldwide & hundreds of scientists now supporting a boycott GMOs until long term scientific studies are conducted. At the very least American consumers have the right to know if GMO ingredients are in a product. This article is bows to the Monsanto party line of pseudoscience rhetoric protecting it’s investments at all costs! How can we trust with our lives, a chemical company turned food Goliath that lies about it past products as safe, like agent orange? Please offer an equal position rebuttal by the OCA & I will remove my objection & continue my respect for giving your readers an honest perspective. Respectfully, JK Kunesh